I am a mortgage broker and real estate investor in Philadelphia and I would like to answer a few of your questions.
-The mortgage you obtain on this duplex will not prevent you from obtaining another mortgage down the road. Your qualification is based on your income, credit and your debt to income ratio. Lenders will look at the total amount of rent you collect on an investment property, minus 30% for expenses and the remainder is counted as income for you. So if your investment property shows an income after subtracting 30% it's counted toward your gross income, if it shows a loss after subtracting the 30% it is counted as debt. Each lender sets the acceptable number of mortgages you can have in your personal name, usually that's 10. if you have questions you can find my contact info on my website at: http://www.liveinphilly.net
- You should be concerned as to whether the duplex is currently rented or not. If it is vacant it is likely that the current owners have had difficulty keeping it rented...and you will inheret their problem. If you feel strongly that you can keep the other unit occupied, run some fake test ads on either craigslist.org or in a classified ad in the local paper. It will give you the opportunity to test the response and proper pricing for the unit.
-If you have no experience managing rental property or renters...I strongly recommend purchasing "Down to Earth Landlording" from author Don Beck. He is a local real estate investor and ace property manager who really knows his stuff.
Good luck to you, and remember that property management, managing renters is a business and carries with it similar risks and rewards. Prepare yourselves and it will be the best thing you have ever done.
I have a young couple (mid 20's) that did just what you described. They rent out the left side and are very blessed with renters that pay on time every time and are there only in the evenings. They have totally remodeled the right side where they live. The renters pay 5/8 of their mortgage (including taxes/insurance) and pay their own utilities. They bought this duplex 1.5 years ago and have since also bought a triplex and a fourplex. These are not people that have a lot of money. They are just investing in real estate the smart way..buying low, remodeling what they can on their own, renting to good people and buidling equity. Everything involves some degree of rist, but the rewards can be very great too. Check in with your CPA as well and get his/her advice.
My husband and I plan on doing some of that this year as well. Best of luck to you.